RB26 Vacuum at highway speeds

[Nesquick]

Hey guys,
I seem pull very little vacuum while on the highway (-.2x100 KPA). Do RB26s create little vacuum?
When idle or taking off of the throttle it stays at a solid -.7*100 KPA

To maintain a constant speed on the highway I stay at -.2*100 KPA, but whenever I want to speed up, it needs to boost which is kind of annoying and a gas guzzler.

RB26 Engine with GT3582r turbo.
G/M 3.5 BAR MAP Sensor
Vacuum Block located with a T-off from brake booster after check valve. Block goes to MAP sensor, WG, WG Control Box, Boost Controller + gauge (last 2 are tee'd in the dash)
The nipple off the intake plenum (Front most cylinder) is routed to my BOV, and the vacuum tube at the front is routed to my FPR. The one at the rear of the vacuum tube engine is blocked off (OEM boost gauge source)
The two pipes going down off the vacuum tube go to the IACV and the other goes to a piece that I forget the name of
Everything else is capped off.

Is this all proper? Or could something in my tune be the culprit? Still running a very mild break in tune on 7PSI.

Thanks for any input

[RRRRB]

Are you running aftermarket cams??

[Nesquick]

Nope. Got the Nissan symbols on the cams

[julio]

If you can't maintain highway speeds while only pulling 10 in*hg, it sounds like you have a lack of power issue. Due to the comment of your break in tune, you had the motor rebuilt? If so, who put the engine back together? I would check your engine error codes, cam timing, and ignition timing if you are having a lack of power issue.

[Nesquick]

Yeah I rebuilt the motor. A reputable shop in my area built it for me. Its the place where all the performance shops send their motors for building. I gotta figure out how to check error codes via AEM S2. The car does maintain a constant speed around -.2 and -.1but as soon as I need to pass someone it needs boost. I'll play around with tyw CAS and check timing again.

[Nesquick]

Alright guys, after talking with a few mechanics and a few cases of beer later we have come to the conclusion that i have a vacuum leak somewhere. I am currently in the process of making a pipe with an air fitting to pressurize the intake manifold to make sure none of the gaskets there are leaking (they shouldn't be, used brand new gaskets when putting the engine back together). Also going to pressurize the IC and piping to see if there is a leak there. Car is holding -7.7PSI (according to AEM tuner) at idle and 0.0-0.1PSI with engine not running.

Just so im not crazy, I have taken pics of all the the vacuum stuff I have set up thus far. Where/What am i missing?

OEM Boost gauge source capped (Rear of balance tube)


Front of Balance Tube going to FPR, whilst the other line is going down to BOV


The EVAP canister lines are completely open to atmos (not being used at all)

VAC Block going to WG, wastegate control box, boost controler, MAP sensor,


AAC Valve looks pretty blocked off to me



Besides a leak in the IC/Piping and manifold, where else could I look?

[julio]

That's strange, your idle vacuum is where it should be.

I use a PVC cap that slips over the turbo inlet coupler that has a hose fitting threaded into it. As long as you use a t-bolt clamp, you can take a large sized air compressor, bring the compressor down to 10psi, hook it up to that fitting, listen/feel for leaks, and bring the pressure up with the compressor until you're happy.

[Nesquick]

Just finished rigging up a 4" pipe to use with my compressor. Testing all that tonight. Let you know how it goes

[Nesquick]

Well, figured out where the problem is.... EVERYWHERE.

AAC valve leaks, between manifold and butterfly valves, few capped off hoses leak, and...... whoever had the engine in japan thought that crimping a hard line would prevent leaks.... NOPE. Nice strong breeze coming out of it.'

Well.... time to get a greddy intake manifold, and convert to single throttle body (possibly). Only looking for ~600HP.
OH, and if anyone has a WORKING aac valve for an RB26, ill definitely take it off your hands for you.


Thanks again for all the help.